Gear pump



1955 J. R. ALBRIGHT ET AL 2,714,857

GEAR PUMP Filed Sept. 4, 1951 2 Sheets-Sheet 1 I {given/0211' a rm 1955 J. R. ALBRIGHT ET AL 2,714,857

GEAR PUMP Filed Sept. 4, 1951 2 Sheets-Sheet 2 J7me A 78 r or:

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United States Patent GEAR PUMP John R. Albright and Swan E. Larson, Rockford, Ill., as-

signors to Geo. D. Roper Corporation, Rockford, Ill., a corporation of Illinois Application September 4, 1951, Serial No. 244,888

2 Claims. (Cl. 103128) This invention relates to gear pumps.

It is an object of this invention to improve the capacity of gear pumps and at the same time reduce to a minimum the noise caused by such pumps during their operation.

Another object of this invention is to provide a gear pump construction in which the length of the gears is made large relative to the diameter of the gears, thereby effecting increased fiuid displacement by the pump with minimum noise in the operation of the pump.

Another object of this invention is to provide in gear pumps novel bearing members for the pump shafts which support the latter intermediate their lengths and facilitate the practical use of a plurality of gears on each pump shaft.

Still another object of this invention is to provide a gear pump of increased gear length to provide helical wrap around of the pump gears even though the gears are formed with a. low helix angle.

It is a specific object of this invention to provide in a gear pump bearings for the pump shafts which also serve as alignment locaters for adjacent abutting casings, which house individual pairs of gears, and as spacers separating the gears on each pump shaft.

Another specific object of this invention is to provide in a gear pump bearings for the pump shafts which support the latter intermediate their lengths within a single casing and which serve as spacers separating the gears on each pump shaft.

Other and further objects and advantages of the invention will be apparent from the following description of preferred embodiments thereof, illustrated in the accompanying drawings, wherein:

Figure l is a top view, partly in section, of a gear pump according to the present invention having a pair of abutting casings, each housing a pair of gears;

Figure 2 is a longitudinal section of this gear pump, taken along the line 22 in Fig. 1;

Figure 3 is a longitudinal section of another form of the invention, in which two pairs of gears are housed .within a single casing;

Figure 4 is a perspective view of one of the combination pump shaft support members employed in both forms of the invention; and

Figure 5 is a section along the line 5-5 in Fig. 2.

In the present invention, advantage is taken of the beneficial results which accrue from extending the length of the gears in a gear pump without at the same time increasing the gear diameter. As is understood by those skilled in the art, the displacement of a gear pump is determined by the volume of the space between the gear teeth and the frequency at which the fluid is expelled from between the gear teeth. Also, it is known that the noise made by a gear pump increases as the pitch line velocity of the gears isincreased. In turn, the pitch line velocity is proportional to the gear diameter, as well as to the speed of rotation of the gears. In accordance with the present invention, pump noise is-minimized by maintaining a relatively small gear diameter, so as to decrease ice the pitch line velocity of the gears. At the same time, the gear length is made relatively large so as to establish the volume of the space between gear teeth at a value sufficient to achieve the desired displacement of fluid by the pump. Thus, for a desired displacement and shaft speed of the pump, the operational noise of the pump can be reduced to a minimum by upsetting the length-todiameter ratio of the gears from what is conventional practice in the art.

In the present invention, the desired increased gear length is facilitated by the provision of novel members supporting the pump shafts intermediate their lengths.

Referring to the form of the invention illustrated in Figs. 1, 2 and 5, there is shown therein a gear pump which is particularly advantageous for operating an hydraulic elevator because of the noise reduction characteristics inherent in the present invention. This pump includes a pair of cases 10, 11 in abutting endwise relation, twoport inlet and outlet manifolds 12 and 13, and face plates 14 and 15 at opposite ends of the case assembly. The inlet ports 12a and 1211 are preferably made Venturi shaped, in accordance with the teaching in U. S. Patent 2,531,726 to Durdin, to supply the fluid to the pump chambers across substantially the entire respective gear faces therein.

A drive shaft 16 is supported for rotation by the face plates 14 and 15, and the idler shaft 17 is fixedly carried by the face plates. The drive shaft 16 carries two gears 18 and 19, disposed respectively within the cases 10 and 11. The first drive gear 18 is pinned to the drive shaft 16 by means of pins 1811., while the gear 19 is keyed to the drive shaft to be slidable axially therealong. Thus, the first gear 18 serves as a locater for the drive shaft 16 for determining the axial position of the drive shaft. However, if desired, other suitable means may be provided for locating the drive shaft axially, and in such event the first gear would be keyed to the drive shaft in the same manner as the other drive gear 19. The fixed idler shaft carries two rotatable gears 20 and 21, positioned to be driven respectively by the driving gears 18 and 19. The drive shaft 16 is driven for rotation by a suitable connection from a prime mover, such as an electric motor.

The face plate 14 abuts against one end face of the case 10, and is formed thereat with apertures 22 adapted to register with corresponding apertures 23 in the adjacent end face of the case It) to receive dowel pins 24. In this manner the axial passage 25 in the face plate is aligned with the pump chamber in the case 10. A bearing bushing 26 is located in the passage 25 immediately adjacent the case 10 to support the drive shaft 16 for rotation. At the opposite end of the face plate 14 a bearing cage 27 is attached by means of cap screws 28 threadedly received in apertures formed in the face plate. The bearing cage 27 includes an annular lip 29 at its inner axial end extending into the axial passage 25 formed in the face plate 14. A collar 30 is secured to the drive shaft 16 and is biased toward engagement with the lip 29 on the bearing cage by means of a coil spring 31, seal washer 32, and seal ring 33. 0 rings 34 and 35 complete the bearing assembly for this end of the drive shaft 16.

At the opposite end of the pump assembly, the case 11 is formed with apertures 36 with which apertures 37 formed in the abutting face of the face plate 15 are adapted to be aligned for receiving dowel pins 38. A hearing bushing 39 is received in an axial passage 40 formed in the face plate 15 and supports the other end of the drive shaft 16 for rotation.

The idler shaft 1'7 is fixedly supported at opposite ends in the aligned axial recesses 41 and 42 formed in the face plates 14 and 15, respectively.

At the abutting faces of the cases 10 and 11, the prescut invention'in'corporate's a pair of spacer-locater-bearing members 43 and 44'whichclose the adjacent ends of the pump chambers within the cases and 11 and serve as supports for the drive shaft 16 and the idler shaft 17. As best seen in Figs. 4' and 5, the upper member 43 is cylindrical throughout most of its periphery and is formed with a flat upper face 46.. When assembled, the members 43 and. 44 are snugly received Within the respective upper and lower pump bores in the cases 10 and 11, and the flat faces 45, 46 ab'ut against each other toprevent each other from turning within the pump bores. As best seen in Fig. 4, the upper and lower pump bores are cylindrical for a major portion of their internal periphery,- at their upper and lower sides respectively. At their intersection, the pump bores are widened so'as to provide continuous front and rear passages 51 and 52 extending the entire axial extent of'th e pump bores. Thus, the support members' 43, 44 do not completely separate the pump chamber in which the gears 18, operate from the pump chamher in which the gears 19, 21 operate.

The upper bearingmember 43 carries a bearing bush-. ing 47 for rotatably supporting the drive shaft 16; Radial grooves 48 are formed in the end faces of the member 43 and communicate with radial grooves 49 in the bearing bushing 47 leading to axial lubrication grooves 50' there- The lengths of the gears and the dimensions of the spacer-locater-bearing members are such that the gears 19 and 21 have a limited amount of axial play within the case 11.

With the described assembly, it will be seen that the length of the driving gear of the pump is the sum of the lengths of the gears 18 and- 19, and the driven gear of the pump has a length equal to the combined lengths of the gears 20' and 21. While two cases have been shown in abutting relation, it is'to be understood that any convenient desired number of cases, may be placed end to end, with the locater members disposed the'rebetween, so as to increase correspondingly the length of the pump gears. Thus, the displacement of the pump may be in creased to the desired value by increasing the, gear length, rather than by using larger gears which would greatly increase the operational noise of the pump. Inaddition, for a desired increase in the pump displacement, increasing the gear length to accomplish this result would not increase the physical size and weight of the pump to the same extent as increasing the gear diameter for that purpose. Each of the pairs of spacer-locater-bearing members between adjacent cases serves to take up the load of the pump shafts, which increases with increasing gear length.

The spacer-locater-bearing members 43, 44 perform a plurality of functions in the assembly of Figs. 1 and 2, since they serve as supports for the pump shafts and maintain the latter in alignment with the pump chambers in the respective cases and with the bearings for either end of the pump shafts in the respective face plates, as spacers for. determining the respective axial positions of the gears within each case, and as locaters for maintaining the cases in alignment when assembled. The necessity for a single pump case having a long bore is avoided because of the facility with which a plurality of relatively short cases may be placed end-'to-end, using the spacer-locater-bearing members 43, 44 of the present invention.

Preferably all of the pump gears are helical, so as to smooth out the displacement of fluid by the pump and avoid pulsating flow. The increase in the gear length by the above-described construction results in an overlap of the gear teeth over the axial extent of the pumping elements. As shown in Fig. 1, helical gear overlap can be achieved over the axial extent of the gears on each shaft even though the helix angle used is such that no overlap occurs on each individual gear. Because of this, a. much smoother flow through the pump is obtained, even though only a standard small helix angle of the gears is employed, such as ten degrees. The small helix angle is, of course, much to be desired because of the resulting low end thrust loads.

The assembly of Figs. 1 and 2 has been found to be particularly advantageous when used as an hydraulic elevator pump unit because of the extremely low noise level for the relatively large output of the pump.

In Fig. 3 there is illustrated a second form of the present invention, embodied in a pump having a single case. The pump case includes a housing having a crosssectional shape similar to that of the individual cases 10, 11 in the Fig. 1 embodiment and transverse, annular, outer end flanges 56 and 57. An end plate 58 is attached to the case at the flange 56 and is formed with spaced axial bores 59, 60 which receive bearing bushings 61, 62 for respectively rotatably supporting the drive shaft 63 and the idler shaft 64 at one end. The other end plate 65 is attached to the case at the flange 57 and similarly carries bearing bushings 66 and 67 for supporting the other ends of the drive shaft and the idler shaft. The drive shaft 63 is driven for rotation by a suitable prime mover, such as a motor.

Carried on the driving shaft 63 are a pair of helical drive gears 68- and 69 spacedapart along the length of the drive shaft. The first drive gear 68 is pinned to the drive shaft, and the other gear 69 is keyed to the drive shaft to be slidable axially therealong, for the same purpose as in the Fig. 1 embodiment of the invention. A corresponding pair of helical idler gears 70, 71 are carried on the rotary idler shaft 64 and mesh with the driving gears to be driven thereby.

Between the pairs of gears are located multi-function support members 72 and 73 of the configuration shown in Fig. 4. The members, 72' and 73 are generally cylindrical in configuration with cut-away, flat, abutting lower and upper faces 74 and 75, respectively. The support members 72, 73 carry bearing bushings 76 and 77 for rotatably support-ing the drive shaft 63 and the idler shaft 64 intermediate their respective lengths. The members 72, 73 are snugly received; within the pump chamber defined by the case 55 to divide the latter into separate compartments. The'abutting flat faces 74 and on the support members prevent them from turning within the pump bore.

The pair ofgears 69,- 71 have a limited amount of axial play within the pump chamber defined by the support members 72, 73 and the end plate 65.

By this provision of bearings located centrally within the pump bore the gear shafts are adequately supported intermediate their respective ends, and the lengths of the gears may thus, be increased, to increase the pump output. The increased g'ear length not only increases the pump output but also minimizes pump noise and smooths the pump. output because of the: resulting helix overlap of the gears on each shaft. These desirable results are accomplished'by' the Fig: 3 construction without the necessity for pairs. of end. plates between each, pair of meshing gears to separate adjacent pairs of gears. By thus eliminating these extra end plates numerous possible sources of alignment errors are thereby avoided,- such as deviations in the size of the dowel pins for attaching the end plates to the respectivev cases, deviations in the size of the dowel pin holes in'the-end plates and in the cases, spacing errors'between, the bearing holes at the end plates for each case, and spacing; errors from the dowel pin holes to the bearing holes. Since all of these errors could be additive, they could be positively? avoided only by reducing the machining tolerances for the pump assembly to. the point where the cost of the pump would be prohibitive. However, the simplified and novel construction of the present invention localizes the critical dimensional tolerances in thesupport members; so that themachining tolerances are 'no't'too stringent in view of the substantial advantages in the'perforrnance' of the pump having extra length gears;

While there have been disclosed forms of the invention having two pairs of gears, it is to be understood that any convenient number of pairs of gears may be incorporated in the pump, either with a corresponding plurality of cases in end to end relation, as in Figs. 1 and 2, or in it single case as in Fig. 3, without departing from the spirit and scope of the present invention.

We claim:

1. A pump comprising a casing assembly including a plurality of separate housings in abutting end-to-end rel .1- tion, end plates at opposite ends of said casing assembly, said housings each having a pair of axially coextensive intersecting pump bores defining a pair of smooth continuous intersecting pump chambers, a rotary drive shaft extending axially through one of said pump bores in each of said housings, a plurality of axially-spaced toothedgears non-rotatably attached to said drive shaft, each of said gears having a length at least equal to the diameter thereof whereby the overall length of the plurality of gears on the drive shaft is large as compared to the (ii-- ameter of the gears, an idler shaft extending axially through the other of the pump bores in each of said housings and carrying a plurality of axially-spaced toothedgears of a length and diameter equal to the length and diameter of the meshing gears carried by the drive shaft, an outlet port formed at one side of each of said housings adjacent the intersection of the pump chambers and in communication with the gear peripheries at one side of the mesh point thereof, an outlet port formed at the other side of each of said housings adjacent the intersection of the pump chambers and in communication with the gear peripheries at the other side of the mesh point thereof, a common fluid supply manifold communicating with each of said inlet ports, a common fluid discharge manifold communicating with each of said discharge ports, and shaft support members disposed between the endwise aligned gears on each of said drive and idler shafts in close running fit with the adjacent end faces of the gears and supporting the drive and idler shafts intermediate their respective lengths, said support members being formed with cylindrical peripheral surfaces complementary to the internal bores in the pump housings of said casing assembly snugly and slidably received in the adjacent ends of the pump bores in the endwise abutting housings to align the separate housings with each othe;, said supporting members being formed with flat faces extending secantially thereof, said flat faces of the support members abutting each other throughout the length thereof at the intersection of the pump bores to limit turning of the support members within the pump housings.

2. A pump comprising a casing assembly including a plurality of separate housings in abutting end-to-end relation, end plates at opposite ends of said casing assembly, said housings each having a pair of axially coextensive intersecting pump bores defining a pair of smooth continuous intersecting pump chambers, a rotary drive shaft extending axially through one of said pump bores in each of said housings, a plurality of axially-spaced toothed-gears non-rotatably attached to said drive shaft, each of said gears having a length at least equal to the diameter thereof whereby the overall length of the plurality of gears on the drive shaft is large as compared to the diameter of the gears, an idler shaft extending axially through the other of the pump bores in each of said housings and carrying a plurality of axially-spaced toothed-gears of a length and diameter equal to the length and diameter of the meshing gears carried by the drive shaft, an inlet port formed at one side of each of said housings adjacent the intersection of the pump chambers and in communication with the gear peripheries at one side of the mesh point thereof, an outlet port formed at the other side of each of said housings adjacent the intersection of the pump chambers and in communication with the gear peripheries at the other side of the mesh point thereof, a common fluid supply manifold communicating with each of said inlet ports, a common fluid discharge manifold communicating with each of said outlet ports, and shaft support members disposed between the endwise aligned gears on each of said drive and idler shafts in close running fit with the adjacent end faces of the gears and supporting the drive and idler shafts intermediate their respective lengths, said support members being formed with cylindrical peripheral surfaces complementary to the internal bores in the pump housings of said casing assembly snugly and slidably received in the adjacent ends of the pump bores in the endwise abutting housings to align the separate housings with each other, said supporting members being formed with flat faces extending secantially thereof, said flat faces of the support members abutting each other through the length thereof at the intersection of the pump bores to limit turning of the support members within the pump housings, the teeth of said gears being formed with a low helix angle which is insutiicient to provide overlap along the length of one gear and sufficient to provide overlap along the overall length of the gears on each of the drive and idler shafts, said gears being arranged on said shafts with the helices of the gears on each shaft extending in the same direction to provide helical gear overlap along the length of each of said shafts.

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